The strong growth in demand for portable consumer electronics is driving the need for high-capacity storage devices. Non-volatile semiconductor memory devices are becoming widely used to meet the ever-growing demands on digital information storage and exchange. Their portability, versatility, and rugged design, along with their high reliability and large capacity, have made such memory devices ideal for use in a wide variety of electronic devices, including for example digital cameras, digital music players, video game consoles, PDAs, and cellular telephones.
While many varied packaging configurations are known, flash memory storage cards may, in general, be fabricated as system-in-a-package (SiP) or multichip modules (MCM), where a plurality of die are mounted and interconnected on a small footprint substrate. The substrate may, in general, include a rigid, dielectric base having a conductive layer etched on one or both sides. Electrical connections are formed between the die and the conductive layer(s), and the conductive layer(s) provide an electric lead structure for connection of the die to a host device. Once electrical connections between the die and substrate are made, the assembly can be encased in a molding compound, which provides a protective package.
In order to most efficiently use package footprint, it is known to stack semiconductor die on top of each other, either completely overlapping each other with a spacer layer in between adjacent die. In an offset configuration, a die is stacked on top of another die so that the bond pads of the lower die are left exposed. An offset configuration provides an advantage of convenient access of the bond pads on each of the semiconductor die in the stack.
As semiconductor die become thinner, and in order to increase memory capacity in semiconductor packages, the number of die stacked within a semiconductor package continues to increase.